Overriding a bp file not in bp-default

I’d like to modify the text on the Create a Blog page (in bp-blogs-templatetags.php), including the mods in my child theme somewhere. I can’t figure out how to do so without actually changing the BP file (which ain’t so good ‘cuz I’d have to add the changes every time I update BP).

Anybody have any clues for a php newbie? I can’t code php yet, but I’m darn good at copy/paste